Electric and hybrid vehicles employ a battery pack, generally incorporating a high voltage battery rated at 300 volts or above, for storage of electrical energy. The power from such a battery pack may be applied to an electric motor, a traction motor, for propelling the vehicle. These battery packs, are intended to convey to the vehicle an appreciable useful range and consist of a plurality of individual cells appropriately connected together in series and parallel to satisfy the voltage and energy storage requirements. Typically such battery packs also include systems to monitor and control the battery condition, including its state of charge, as well as high-voltage contactors and bus bars for charging and discharging the battery pack. Battery packs are often confined in a lightweight, non-structural casing and may also include provision for cooling to maintain the batteries in a preferred operating range.
Even with the use of higher power density batteries employing advanced battery chemistries, for example lithium ion batteries, the mass of such battery packs may be appreciable and constitute a significant portion of the vehicle mass. Adding to the overall contribution to vehicle mass is the need for an enclosure consisting of a tray, or similar support structure, and a cover to secure the battery pack in the vehicle. Of course, such enclosures must be suitably robust and stiff to accommodate, in addition to static loads, the dynamic loads which will occur in service. Further, these structural enclosures must be compatible with adjacent chassis or body members of the vehicle.
Battery pack enclosures have been fabricated from steel or magnesium. But steel, with its relatively high density adds more vehicle mass than desired, and magnesium, though of low density, is prone to corrosion if exposed to aqueous environments, and has limited ductility. There is therefore a need for a robust, low density, battery pack enclosure.